Production of plasminogen activator from cells to which lectin is added to the culture medium

Abstract

Increased yields of enzymes, particularly tissue plasminogen activator (tPA), are produced from cells, particularly CNCM I-222 cells, by a process using less concentrated lectin, particularly concanavalin A, in culture medium added to replace initial growth medium than has been used hitherto. After first harvesting of enzyme in supernatants, the culture can be reactivated by the addition of fresh culture medium containing an even lower lectin concentration, and a further harvest of enzyme obtained. The two harvests of enzyme together can give a greater overall yield than a single harvest after a single induction step employing the conventionally used higher lectin concentrations. Enzyme yield can be further increased by repeating the last incubation step once or twice to obtain one or two further harvests.

We claim: 
     
       1. A process for the production of tPA from CNCM I-222 cells, comprising incubating cells in culture medium at about 36.5° C. for about 72 hours to produce growth of the cells; removing the growth medium; adding a further supply of fresh culture medium containing concanavalin A at a concentration about but no exceeding 20 micrograms/ml but containing no serum; incubating the culture at about 36.5° C. for about 48 hours, resulting in production of tPA from the cells; harvesting supernatants including the tPa; adding to the culture after harvesting of the supernatants a further supply of fresh culture medium containing concanavalin A at a concentration of about 5 micrograms/ml but containing no serum; incubating the culture at about 36.5° C. for about 48 hours, resulting in production of tPA from the cells; and harvesting supernatants including the tPA.